Method of manufacturing commutators



April 8, 1952 P w, NIPPERT 2,592,172

METHOD OF MANUFACTURING COMMUTATORS Filed June' 15, 1947 reductionwithin a restricted throat;

Patented Apr. 8, 1952 METHOD OF MANUFACTURING COMMUTATORS Paul W.Nippert, Columbus, Ohio Application June 13, 1947, Serial No. 754,427

The present invention relates to the production of commutators forelectrical motors and similar dynamo-electric machines.

Heretofore, in the production of commutators, various methods have beenemployed to provide a commutator formed from a plurality of radiallypositioned brush-engaging segments separated by means of insulatingmaterial disposed between adjacent segments. The primary objective inthe production of commutators of this type is to provide means wherebythe individual segments and insulation material are prevented fromdisplacement or detachment from the commutator body when the same isundergoing rotation at relatively high speeds. Further, the com mutatormust be capable of withstanding relatively heavy wear, occasioned by thefrictional engagement of the outer surface thereof with the associatedcommutator brushes, without disintegration or displacement of theindividual segments thereof. Many of the previously employed methods ofconstructing commutators have realized the objectives heretoforeoutlined, but such methods were generally characterized by relativelyhigh production costs and expenditure 4 of labor. It follows therefore,that the-general object of this invention is to provide improved methodsfor the construction of dynamo-electric commutators, and decreases thelabor time ambient to such production.

Another object of this invention is to provide improved and efiicientmethods for the construction of commutators which provides efficientmeans for maintaining the individual brush engaging surfaces or segmentsin insulated order, and which embodies means whereby these segments areheld in a compressed and compact state against separating forcesimparted by high speeds of rotation during operation.

' These and additional objects and advantages of the method set forth inthe present invention will become more readily apparent with referenceto the following detailed description and the accompanying drawingswherein:

Figure 1 is an elevational view of an assembled sheaf of alternatelyinsulated commutator bars, and illustrating the initial step in themanufacture of commutators formed in accordance with the methodspresented in this invention.

Fig. 2 is a vertical sectional view taken through the sheaf ofcommutator bars as the same is undergoing insertion within a work tube;

Fig. 3 is a vertical sectional view illustrating the sheaf undergoingcompaction and diameter 3 Claims. (01. 29-155.54)

", ually operated press indicated by the numeral Fig. 4 is a sideelevational view illustrating the steps of cutting the compacted portionof the sheaf into individual commutator annuli;

Fig. 5 is a diagrammatic view illustrating the commutator annulusundergoing machining operation;

Fig. 6 is a vertical sectional view taken through a machined annulus asthe same undergoes abrasive action in the presence of a sand blast;

Fig. 7 is an elevational view of the machined annulus positioned withina work ring;

Fig. 8 is a transverse vertical sectional view taken through a completedcommutator formed in accordance with the present invention.

The first step in the construction of commutators formed in accordancewith the present invention, is to assemble into sheaf like formation aplurality of elongated longitudinally disposed commutatorsegment-forming bars 8 with strips of insulation edisposed betweenadjacent bars. It will be understood that each of the commutator segmentbars possess a substantially V- shaped cross-sectional configuration,and have their. upper edges rounded in order that a substantiallycontinuous circular sheaf may be formed. The strips of insulationinterposed between adjacent bars are of substantially normal rectangularconfiguration, and may be formed from any suitable insulating materialsuch as mica, paper or various other dielectric compounds. To facilitatethe assembly of the assembly of the individual bars and strips ofinsulation, a circular cross-sectional shaft or tubular core I2 isprovided to form the axial opening of the sheaf. The individual bars andinsulation strips are stacked either by hand or mechanical operationaround the outer surface of the central shaft to form the tubular sheafbearing the numeral [0, and possessing a substantially circularcross-sectional configuration. After the initial assembly of therequired number of bars and strips of insulation, use is made of aplurality of clamping rings II which serve to hold the individual barsand insulation in stacked arrangement upon the axially disposed formingtube l2, and to prevent separation of the bars during handlingoperation.

The secondstep in the formation of the commutator annulus, consists inplacing or pressing the assembled sheaf [0 into a metallic work tube l3,and simultaneously removing the axially disposed core l2 and the outerclamping rings II. This, operation, as shown in Fig. 2, may be easilyaccomplished by means of a hydraulic or mancommutator annulus. and thesheaf I are positioned within the form- M. It will be understood, thatthe pressing of the preformed sheaf within the tube l3 serves only toinitially shape the sheaf into a substantially true circular form. Inpressing the stacked sheaf into the work tube 13, the individual copperbars and strips of insulation are initially positioned in substantiallyclosely fitting radially disposed order, and all unnecessary spacing andirregularities between bars and strips of insulation are eliminated.

The third step in the construction of the commutator annulus is depicteddiagrammatically in Fig. 3 of the drawing, and consists in placing thepreformed sheaf, positioned within the work tube [3 within a formingtube l5 which is formed at one end with a tapered and relativelyrestricted throat IS. The tube [5 is formed with a tubular chamberadapted to receive in closely fitting order the outer surface of thework tube l3, and the restricted throat I6 is formed at its inneropening to correspond in size to the outer diameter of the preformedsheaf I0, whereas the outer opening of the restricted throat possesses adiameter which is relatively less than the diameter of the preformedsheaf, and which, corresponds to the desired diameter of a finishedAfter the work tube [3 ing tube IS, the end portion of the sheaf I0 isforced outwardly through the restricted throat, preferably by means of ahydraulic ram indicated at H, in order to reduce the outer diameter ofthe end portion of the sheaf, and at the same time compacting orcompressing the individual segment bars and strips of insulation intoclosely and tightly fitting order. It will be understood, that due tothe general wedge-shape of the individual commutator bars, the borediameter of the sheaf will only be slightly decreased, with thecompaction taking place largely between the individual segments toarrange the same in closely and tightly fitting order. Also theextrusion of the compressed portion of the sheaf is preferablyintermittent in order that a portion corresponding in width to that of afinished commutator annulus may be extruded with one application ofpressure of the hydraulic ram l1. Simultaneous with the operation ofextrusion of the compressed portion of the sheaf, is the application ofa retaining ring I 8 to the outer surface of the extruded portion. Asdepicted in Fig. 4, the retaining ring [8 is held adjacent the openingof the restricted throat I 6, by means of a second hydraulic ram l9carrying upon its outer end a socket adapter 20. The

sequence of operation of the two hydraulic rams l1 and I9 is such thatthe retaining or work ring I8 is applied adjacent the opening of therestricted throat l6 just prior to the extrusion and compression of theend portion of the commutator sheaf, and as the latter moves outwardlyfrom the restricted throat the compressed segments are held within thebore of the ring and prevented from splaying outwardly.

The next step in the operation consists, as shown in Fig. 4, intransversely cutting the compressed portion, which is held within thework ring I, from the body portion of the sheaf. This may beaccomplished by means of applying rotation to the forming tube I5 whichproduces a relatively high speed rotation within the sheaf, at whichtime a cutting edge 2! may be brought into engagement with thecompressed portion of the sheaf, extending from the restricted throat IEto effect severance thereof. Upon severance a commutator annulus of thedesired length is formed, which annulus is held within the bore of thework ring [8. The operations of extrusion and applying of the work ring18 are repeated until a number of annuli or rings are formed from theassembled sheaf, and when relatively high speed machinery is utilized inthese combined operations, a relatively large rate of output isobtained. After the complete removal of the sheaf from within the worktube l3 by the operation of the hydraulic ram l1, the work tube is thenremoved from the forming tube [5, and a similar tube containing anotherpreformed and assembled sheaf is inserted whereupon the operation may berepeated.

After severance of the compressed and compacted annulus, indicatedgenerally by the numeral 22, the same is placed with its work ring l8upon a lathe, or other suitable revolving instrument, and machined, asdepicted in Fig. 5, to form annular dove-tailed grooves 23 in the endfaces of the annulus. These dove-tailed grooves form a seating regionabout the bore of the annulus, the functions of which will behereinafter more fully described.

The penultimate step in the production of commutators in accordance withthis invention, consists in removing burrs or smears of copper from theouter surfaces of the machined annulus. It will be noted, that inmachining the annulus to form the dove-tailed grooves 23, minute ormicroscopic particles of copper are imbedded within the strips ofinsulation disposed between the adjacent copper segments, and if suchparticles are allowed to remain in the insulation, the dielectriceificiency thereof is greatly reduced, and in many instances thecommutator will fail to withstand operating voltages without arcingbetween adjacent segments, which results in the overall failure of thecommutator. To insure against this contingency, the outer or machinedsurfaces of the annulus are subjected to an abrading action to removethe machined particles of copper. A sand blasting operation, asillustrated in Fig. 6, has been found very efficient in effecting theremoval of such particles, but it will be understood, that this abradingstep is intended to include not only sand blasting operations, but anymechanical means of removing the machined or smear over particles ofcopper by abrasive action, such as subjecting the annulus to acarborundum blast, or to the flow or blast of a liquid, such as water,which contains an abrasive compound or element. By such operation, it isonly necessary that the annulus be subjected to the abrasive for arelatively short period of time, approximating five seconds. During thesand blasting operation, the exterior surfaces of the dove-tailedgrooves 23, while appearing to be smoothed, are actually roughened to aslight degree, which is an advantageous feature, in that a moreefficient frictional union may be had between the copper segments andthe layer of insulation interposed between the in dividual segments andthe metallic fastening devices subsequently utilized to hold thesegments and strips of insulation in their annular disposition, to behereinafter more fully described.

Upon completion of the sand blasting operation, the annulus must beprovided with a permanent fastening means for joining the individualcopper segments and insulating strips to firmly hold the segments of theannulus in their compacted and true circular disposition, and to preventdisplacement of the segments or insulation upon removal of the work ringl8. To this end, a circular and tubular core 24, provided upon its outersurface with a layer of insulating material, is introduced Within theaxial bore of the annulus. The core 24 may be provided at one of itsends, as shown in Fig. 8, with an integrally formed circular end ring 26which in turn is formed with an inwardlly directed annular dovetailedprojection 21 adapted for interfitting engagement with one of thedove-tailed grooves 23 formed in the end faces of the annulus. In thiscase, the opposite end of the core 24 receives a free end ring 28 formedsimilarly to the first end ring 26, and provided with an inwardlyextending annular projection 29 which engages the dove-tailed groove 23formed in the opposite end face of the annulus. After the core and itsend rings have been positioned with respect to the annulus, the end ofthe core which receives the free end ring 28 is flared or flangedoutwardly as at 39, by a suitable revolving head, not shown, to firmlyand rigidly lock the end rings within the respective dove-tailed groovesof the annulus, and to prevent subsequent removal of the free end ring28. It will be understood, that the entire outer surfaces of the coreand the end rings are provided with layers of insulation in order toprevent contact with the copper segments. It will also be understood.that the end ring 26 need not be formed integral with the core 24 toaccomplish the desired union of the individual segments, but may befreely positioned upon the core, as in the case of the free end ring 28,in which case, it would necessarily follow that both of the ends of thecore would be flared to firmly lock the rings within the dovetailedgrooves and prevent separation from the core. In view of theinterfitting engagement of the annular projections 27 and 29 with thedovetailed grooves 23, it will be seen that a w dgelock is provided foreach of the copper segments and the intervening strips of insulation,whereby the latter are prevented from becoming displaced eitherlaterally or radially during subsequent operations, and it will here beunderstood that the term displacement is intended to include anyrelative movement of the individual segments of the commutator of theorder of one-thousandth of an inch or more, otherwise, such displacementwould result in defective commutator action.

After flaring the end of the core 24 to eff ctively lock the individualsegments of the annulus, the Work ring [8 is removed from the annul-uswithout fear of separation, and the annulus is now ready forinstallation upon the shaft of an electric motor or similar machine.

In view of the foregoing, it will be seen that the present inventionprovides eificient and time saving methods for constructing commutatorswhich possess improved characteristics ambient to their operationalfunctions. By the passage of the preassembled sheaf of commutatorsegment forming bars through the restricted forming tube, the individualbars and intervening strips of insulation are compacted or compressedinto tightly fitting order, and by the placement of the continuous workring around the annulus, the individual segments are firmly held in sucha compacted state until the permanent locking core is installed.Further, in subjecting the machined surfaces of the annulus to theabrasive action of a sand blast, all burrs and microscopic particles ofcopper which have become imbedded within the insulation during or beforemachining operations are efficiently removed to insure proper andefiicient dielectric function of the insulating strips, and to preventgaping between the individual commutator segments.

I claim:

1. In the construction of commutators, those steps which compriseassembling a plurality of elongated segment-forming strips withintervening strips of insulation into tubular sheaf formation in anencircling holder, axially forcing the sheaf from the holder andcontinuously subjecting the sheaf While being forced from the holder toinwardly and radially applied forces to produce compaction and reductionin diameter thereof, successively applying a retaining ring aroundsuccessive end portions of the sheaf after the diameters thereof havebeen thus reduced, and transversely cutting successive reduced endportions from the body of the sheaf following the insertion of eachreduced end portion within a retaining ring to continuously andsuccessively form a series of commutator annuli.

2. In the construction of commutators, those steps which compriseassembling a plurality of elongated segment-forming strips Withintervening strips of insulation into sheaf formation in an encirclingholder, the sheaf having an axial bore extending from one end to theother, extruding the sheaf through a circular restriction while forcingthe sheaf from the holder to produce inward radial compaction andreduction in diameter of the sheaf, successively applying a retainingring around successive end portions of the sheaf after the diametersthereof have been thus reduced, and transversely cutting successivereduced end portions from the body of the sheaf following the insertionof each reduced end portion within a retaining ring to continuously andsuccessively form a series of commutator annuli.

3. In the construction of a commutator. those steps which compriseassembling a, plurality of elongated segment forming strips withintervening strip of insulation about a core element to form a tubularsheaf, retaining the strips against radial outward movement, forcing thesegmentforming and insulating strips while held in place by the coreelement into a tube and then removing the core, ejecting the sheaf fromthe tube and continuously subjecting the sheaf while being ejected toinwardly and radially applied forces to produce compaction and reductionin diameter thereof, successively applying a retaining ring aroundsuccessive end portions of the sheaf after the diameters thereof havebeen thus reduced, and transversely cutting successive reduced endportions from the body of the sheaf following the insertion of eachreduced end portion within a retaining ring to continuously andsuccessively form a series of commutator annuli.

PAUL W. NIPPERT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,296,969 Kopsch Mar. 11, 19192,141,268 Dunbar Dec. 27, 1938 2,272,688 McGibbon Feb. 10, 19422,295,338 Ely Sept. 8, 1942 2,318,095 Putnam May 4, 1943 2,376,613Nelson May 22, 1945

